Re: I need a crash course in resolution, DPI, color spaces, etc.
We can\'t get printer and monitor to match exactly because its physically impossible. What color management does is rearrange the color so a 255.0.0 RGB value will be reproduced in the most saturated red the calibrated monitor can display and printed with the most saturated red the combination of yellow and magenta on the printer can produce.
Color management relies on the fact human color perception is highly adaptive. What we perceive is in large part what our brains expect to see based on previous experience. What\'s why a white shirt will look the same indoors and out; the brain rationalizes by comparison with other things the shirt must be white, so it adapts our color perception to make it white.
The same thing happens with primary \"reference\" colors . If we see a red Ferrari in a photo on the monitor or a print and there is not more saturated red in sight them our brains convince us we are looking at the same saturation of red as the paint of the car. But if we compare car, monitor and print side-by-side the brain will key off the more saturated red in the car and the other two will look weak by comparison.
When we profile a device a map of the maximum saturation the device can produce is created. Those maps are used by the computer to know when the max. red in one gamut is different than another, and how to move it. Its done automatically, but we need to select an editing gamut both the camera, monitor and printer gamuts can all fit inside of. The number of discrete colors in the various gamuts is the same and is a function of bit depth. See: http://www.chin.gc.ca/English/Digital_Content/Capture_Collections/Sub_sections/fnd_resolution.html
Color gamuts are three dimensional and their outer boundaries represent the most saturated colors. If you have a Mac you can use the ColorSync utility to compare gamut size and shape as rotating 3D wireframes. Here are some screen shots.
These two compare a 8/C HP printer gamut on high gloss paper the gamuts of AbobeRGB and sRGB:
Here\'s a comparison of the two working gamuts with the gamut of my iMac 24\" monitor
Here is how sRGB and AdobeRGB compare:
As you can see sRGB is a good fit to the monitor. That\'s why sRGB is the de facto standard for web work; it will look similar on most monitors. But note the fit of sRGB vs AdobeRGB with the 8/C inket printer gamut. The more of the highly saturated colors the printer can produce fall mostly inside AbobeRGB but not sRGB. That makes AbobeRGB a better editing space. But since some colors are falling outside of AdobeRGB an even wider working (i.e. editing) space like ProPhoto RGB is better for today\'s 8 and 12 color high-end printers.
If we convert from RAW to ProPhoto to edit we can either convert a copy to sRGB for web use, and print without much, if any loss in color saturation. So the optimal workflow color-wise is:
Shoot RAW
Edit in ProPhoto RGB
Convert to sRGB for copies used on the web
Convert to printer profile or largest working space printer recognizes for prints.
Most ink jets recognize AdobeRGB files and some recognize PhoPhotoRGB. But photo-based printers at places like Costco are set-up for an sRGB workflow. It is also possible to download the printer profiles from Costco, but they aren\'t much different from sRGB:
A simple way to get your bearings on color is take your camera out on a clear sunny day and take a shot of a colorful scene with WB set to \"daylight\". Then without screwing with it, display it on your monitor and print it with the printer managing the color. You might not have a clue about color management, but the people who created your equipment do, so your file should look OK on the monitor (if its calibrated correctly) and look OK on the print. Print will not match monitor, but both should create the same perceptual reaction and look \"normal\".
If you try that empirical test starting with the same RAW file but using different working spaces (sRGB, AdobeRGB, ProPhoto) and compare you\'ll see what, if any, difference they make on your equipment. If you can see a difference it matters, and go with what looks best. If you can\'t see the difference go with what is most convenient
Chuck
Nov 10, 2009 at 11:34 PM
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